In the case such that a construction work of a public water supply pipe is executed, a method is employed that without stopping water on the upstream side, passage of water in the pipe is temporarily stopped by using a gate valve device as a non-water-stop pipe water stopping device while maintaining a water passing state, and a construction work is performed on the downstream side. After completion of the construction work, the water stop state is cancelled.
Conventionally, the volume of a rubber lining in a valve body used as the non-water-stop pipe water stopping device tends to be large. The reason is that since the valve body of a pipe water stopping device is inserted in a buried pipe through which water is passing to stop water, positioning between a bore hole and the valve is necessary at a site. To reliably interrupt the flow of water, the volume of the rubber lining has to be large. That is, stopping of water in a pipe depends on elasticity of the rubber lining.
Pipes in which the no-water-stop pipe water stopping device is installed include a pipe buried and used for long time and a relatively new pipe and the like. The inside diameters of pipes having the same outside diameter are usually different from each other according to the kinds of the pipes. As a result, the volume of the rubber lining has to be increased to enhance the cutoff performance.
To reliably stop water in a pipe at a site, the following conditions have to be satisfied, and the balance has to be adjusted.
(1) The compression force of the rubber lining in the bottom of a valve body and the bottom of the inner face of the pipe is allowed to act.
(2) The compression force of the rubber lining on the side face of the valve body and the side face in the pipe is allowed to act.
(3) The bore hole is closed by an upper part of the valve body.
The conditions (1) and (2) can be satisfied to some extent by increasing the volume of the rubber lining. However, the deformation amount of the valve body increases at the time of cutting off the valve body, and the torque necessary for cutoff since the valve body comes into contact with the pipe bottom until water completely stops tends to increase. When the deformation amount is large, it is difficult to obtain sufficient compressibility with the pipe inner face, so that sufficient cutoff performance cannot be obtained. Consequently, there is a problem such that when the opening/closing operations are repeated, the rubber lining is damaged by the bore hole.
The condition (3) requires to close the bore hole after reliably closing the pipe under the conditions (1) and (2). When the bore hole is closed first, a flange part of the rubber lining comes into contact with the bore hole, the cutoff torque increases, and compression of the valve body rubber lining with the pipe inner face is not transferred. As a result, when the cutoff is further increased, a problem occurs that the rubber lining is damaged by the bore hole.
As described above, the balance among the conditions (1) to (3) has to be adjusted for existing pipes having different inside diameters. For this purpose, a non-water-stop pipe water stopping device having higher cutoff performance is in demand.
The applicant of the present invention has developed the gate valve device disclosed in Patent Document 1. The gate valve device has a spindle and a valve rod to be inserted as a drive shaft into a pipe, and also a movable piece for pressing a seal member against the inner wall of the pipe, so that water can be sufficiently stopped. Moreover, the size in the vertical direction can be made smaller than that of a conventional device (for example, Patent Document 1).
Patent Document 1: Japanese Unexamined Patent Application Publication No. 2003-343748